EP 1 347 154 A2 shows a swivel-type adjuster that is designated to be used with a control shaft of a variable valve train. A first hydraulic rotatable mechanism is connected to a second hydraulic rotatable mechanism so that by choosing a raw adjustment and by choosing a fine tuning adjustment an exact position for an eccenter of the variable valve train can be picked. Accordingly, it can be said that the angular position of the eccenter is depicted by a two-stage system.
U.S. Pat. No. 2,911,956 describes a plate-like shaft positioner by which a swivel movement of a first plate influences the swivel range of a second plate and so forth.
WO 01/12996 shows in FIG. 5a a two stator vane cam phasing system in which a rotor is limited in its swivel movements by rotating first and second stator.
Further, by studying U.S. Pat. No. 5,233,948 a person skilled in the art would realize that many advantages can be found by a camshaft with cams that can be superposed. Consequently, for many years there has been a need to design some kind of phase adjuster that can operate such a camshaft. However, practical solutions that actually work in an engine environment can rarely be found. As in U.S. Pat. No. 5,233,948, many basics are only laid open on a theoretical level but there is no teaching how to make them work in practice.
Attempts how to make such camshafts work can be derived from FIGS. 4a, 4b, 4c of U.S. Pat. No. 5,235,939. In this document, the figures show a coaxially arranged double camshaft with at least two sets of cams which are offset by an angle. The cams are mounted by fastening pins and fastening clips onto the bearing camshaft. A similar embodiment can be found in WO 2005/040 562 A1. The documents teach a type of hydraulic linear cylinder to select certain positions for the cam. Further, a similar design is shown in FIG. 1 of DE 43 32 868 A1. A further linear adjustable device for camshafts is shown in EP 0 397 540 A1. A different system can be seen in FIGS. 5 and 6 of U.S. Pat. No. 4,332,222 in which a contour bearing pin determines the angle of two cams and by that the position of the camshaft. A document that teaches a very simple and light hollow camshaft is DE 36 24 827. The hollow camshaft taught in that document is, however, outdated in the meantime because nowadays both camshafts have to offer a phase adjustment option. Further reasoning for creating a special contour of a cam can be found in DE 199 14 909 A1, which shows an auxiliary cam for adjusting the contour of the main cam with the purpose to control the gas exchange valves a second time. For reasons of completeness, the two documents JP 11 17 31 20 and WO 1992 012 333 are named.
From the foregoing prior art, it can be concluded that for years and years the industry has been looking for a workable design which enables the adjusting of the phasing of occurrences in a gas exchange valve train.
The further graphical representation of a double camshaft can be seen in DE 10 2005 014 680 A1 wherein the graphics stop at the oil distribution bearing. It may be assumed that the Applicant stopped at the point because further components were still needed. The document WO 2005/040562 describes a camshaft with at least two cams. The cams are axially arranged and displaceable. However, the document falls short in teaching how to operate the camshaft in a combustion engine.
A first sprocket and a second sprocket for a cam phaser attached to a hollow camshaft can be seen in U.S. Pat. No. 6,253,719 B1. Instead of arranging both sprockets in parallel, a different design is shown in U.S. Pat. No. 6,725,817 B2. A first cam phaser that is the inner cam phaser is surrounded by a second cam phaser that is the outer cam phaser. In the meantime, it is known from many different car manufacturers that both types of systems do not work as expected. There is a need to enhance the possible angle of adjustment.
U.S. Pat. No. 6,076,492 shows that it is widely known that the alignment of a cam phaser, a cylinder head, and a control valve together with a camshaft in a stationary manner is quite difficult. For example, one difficulty can be found by the canting of the components one to the other.
The described embodiments in the prior art of two offsetable and adjustable gas exchange valve actuation means on one single control shaft have been discussed above to include and incorporate them in the specification in order to enhance the specification and to lead the reader to the more challenging aspects of the present invention.
A gas exchange valve control shaft comprising two camshafts encroaching each other preferably coaxially arranged with the outer camshaft surrounding the inner camshaft, is also referred to as a double camshaft. A double camshaft is a camshaft which is assembled from two pieces. Persons skilled in the art often associate only one single shaft when hearing a camshaft of which all cams are placed in stationary relationship one to the other. A camshaft within the scope of the present invention is a camshaft of one, two or even more camshafts, especially camshafts having the same axle.